Phenolic machines
without difficulty. As a rule, it is machined more readily
than metals on standard machine tools such as those used for wood
or metal fabrication.

For most machining operations, ordinary
high-speed steel tools are satisfactory. However, where production
quantity, production speed or finish are important factors, carbide-tipped
tools often prove more economical. Cutting tools must be kept
extremely sharp to achieve accuracy and fine finish.

Phenolic is machined dry--cutting
compounds and lubricants are not necessary. Cooling by air
is preferable to the use of liquid coolants which are difficult
to remove from finished parts. Machine operators should be
cautioned to keep the temperature of the work below 150°C since
temperature above 150°C may distort the material. Cuttings
are readily removed by suction.

Glass
Base Grades

In many cases,
the same machining operations employed in the fabrication of metals
and wood may also be adapted to glass base grades. However,
certain slight changes in tools and the use of proper speeds are
necessary.

Diamond or tungsten-carbide tools
will give more satisfactory work with longer, more economical life
than high-speed steel tools.

Circular
saws may be used for straight or angular sawing. When smooth
edges are required or close tolerances are important, a hollow-
ground circular saw without set should be used. For rough
cutting, saws with set are satisfactory. Best results are
obtained when the saw blade projects a minimum distance above the
saw table.

12"
saws should be used for material up to 1" thick and 16"
saws should be used for thickness up to 2 1/2". It is
important that all teeth be square, of the same height, and free
from burrs. The cutting edge should run either directly
toward or just back of the center hole. In both circular sawing
and band sawing, the work should be fed as rapidly as possible without
forcing.

Glass
Base Grades

A
diamond impregnated wheel with copper body 1/16" thick and
12" dia. run at 3000-3600 rpm will give good results cutting
dry with a good exhaust system. The material is fed by hand
into the saw as fast as it will cut without forcing the saw.
Idling creates friction and heat, which cause excessive dulling
and burning. A flood of water on the work and wheel can be
used when necessary to prevent overheating. Abrasive wheel
cutting under water is also recommended.

The standard
band saw is satisfactory where close tolerances or smooth edges
are not important. It is most effective in sawing blanks from
plate stock.

Saw blades
should have between 4 and 7 teeth per inch with some set, the number
of teeth depend on the thickness of the material being sawed.
For heavy material, 3" thick and over, a blade with three teeth
per inch is recommended. Operating speeds should be approximately
3000 feet per minute and blades should be tempered to permit frequent
sharpening.

Width of
the blade will vary depending on the radius to be cut. For
circular cuts the widths should be narrow, but for straight cuts
the blade may be up to 1" in width.

Glass
Base Grades

For best
results carbide tipped blades should be used. Work should
be fed lightly and the blade should be kept sharp. Sawing
can be done dry with a good exhaust system.

Standard
shears suitable for sheet metal are recommended in shearing phenolic.
The knife blade should be kept sharp and the material held rigid
with a hold-down bar. Most paper laminates up to 1/16"
thickness and canvas laminates up to 1/8" thickness may be
sheared at room temperature (70°F min).

Glass
Base Grades

Thickness
up to 3/32" can be sheared. The same standard practices
are used as for other laminated plastics.

Turning

Paper
and Fabric Grades

Ordinary
high-speed tool steel can be used in finishing operations for all
phenolic grades. However, carbide-tipped tools may prove more
economical and will hold sizes more accurately from piece to piece.
About .010" stock should be left for finishing. Laminated
phenolic can be turned at 400 surface feet per minute with high-speed
steel tools, and about twice that fast with carbides. Tools
should be kept sharp, ground with an included angle of 80° to 100°,
and with a 10° to 16° side clearance. Cutting should be done
dry.

Glass
Base Grades

Conventional
machining, such as turning, boring, and facing can be done on automatic
screw machines, standard and production lathes and hand turret lathes.

Carbide-tipped
tools and cutters should be used with surface speeds below those
used for paper base laminates. Tools should be ground with
a zero rake and machining can be done dry with an exhaust system
to remove dust. A coolant can be used, but is not necessary.

Standard
tools may be used at speeds and feed similar to those for bronze,
and soft steel. It may be more economical in spite of higher
material cost to use carbide tools. The cutting angle of the
mill will give better results if ground with a slight rake.

Glass
Base Grades

Glass base
laminates can be milled very satisfactorily on any conventional
metal-working milling machine. Carbide tipped tools should
be used. Only climb or down milling should be practiced, as
up milling will tend to delaminate the material.

Drilling
and Tapping

Paper
and Fabric Grades

A standard
high-speed drill with lips backed off to provide plenty of clearance
is satisfactory for all phenolic grades. However, for long
production runs and deep holes, carbide-tipped drills give the best
performance.

Drills
should be lifted from the work frequently to prevent binding and
excessive heating. The feed should be light and uniform and
the speed of the drill should be considerably in excess of that
used for soft steel. With tungsten-carbide tips, speeds may
be as high as 16,000 rpm. Where possible, the material being
drilled should be backed up with scrap phenolic or other soft material
to prevent chipping out.

In drilling
phenolic parallel to laminations, extra care must be taken to prevent
splitting. The material should be clamped in a vise or between
plates and the drill should be lifted more frequently to remove
chips.

Holes 3/4"
and over may be drilled in the conventional manner using radial
drill presses or the counterbore method in which a pilot hole is
drilled first.

Drill size--
Because of the nature of plastic material, the diameters of holes
drilled in laminates are usually .002" under the drill size.
Therefore, the drill selected should be at least .002" larger
than the specified diameter of the hole. If the drill is being
used dull, the hole size may be an additional .002" undersize,
or a total of .004" less than the diameter of the drill.

The recommendations
for drilling also apply to tapping. Taps used for metal are
also suitable for Phenolic. Tapping heads or tapping machines
may be used, and for production work, collapsible taps are available
in sizes over 1 1/4".

Tap
Size

In tapping
phenolic, high-speed taps .002" oversize should be used.
The tap drill size should also be changed to .002" oversize
to counteract the tendency of the drill to cut undersize.
If the thread is to be used frequently, metal inserts should be
used.

For threaded
holes over 1/2", it is often more desirable to chase the thread
on a lathe using a motor-driven cutter mounted on the tool post.

When drilling
glass base grades, a carbide drill should be used. The materials
can be drilled dry with a good exhaust system to remove dust.
A flood of water on the work and drill can be used when necessary
to prevent overheating and dulling of drills. High speed drills,
nitrate treated, can be used, but must be sharpened more often.
Care should be taken when sharpening that the drill is cut back
far enough to original body diameter of drill. Spindle speed
for these grades is 4800 rpm for 1/4" diameter drills.

The methods
for tapping these materials are much the same as for tapping paper
base laminated plastics. The abrasiveness may cause taps to
cut very close to size, resulting in a tendency toward binding when
backing out. Standard high speed steel taps can be used on
short runs. For any sizeable quantity carbide taps should
be used. Taps should be purchased oversize. Coolant
can be used, but is not necessary if a good exhaust system is available.